Resinous polyamide composition and process of preparing the same



fiid States i atent Q RESINOUS POLYAMZDE CflP/EPOSZTGN Al -5.3 PRGCESS 0F FREPARENG THE No Drawing. Application November 3 's, Serial No. 395,264

8 Claims. (Cl. ere-er The present invention relates to a novel resinous polyamide composition which is particularly adapted for use as an adhesive and to the process of preparing the same.

The invention disclosed herein is related to and an improvement of the invention disclosed in copending application Serial No. 385,887 filed October 13, 1953, in the name of James H. Groves.

The composition of the present invention is composed of a blend of a hard and tough polyamide resin derived by the condensation of an aliphatic polyamine with a mixture of acids including polymeric fat acids, and a softer tacky polyamide resin made by the condensation of a polyalkylene polyamine with polymeric fat acids. This blend of polyamide resins is then subjected to a heat treatment, which serves to modify the chemical and physical properties of the composition such that a composition particularly adapted for use as an adhesive is obtained.

It is therefore an object of the present invention to provide a novel resinous polyamide composition that is particularly adapted for use as an adhesive.

It is also an object of the present invention to provide an improved polyamide adhesive composition in which the improvement is due principally to the heat bodying of the polyamide resin constituting the major proportion of the composition.

It is another object of the present invention to provide a tough flexible, resilient, polyamide composition which is heat stable and solvent resistant andwhich is composed of a blend of two different polyamide resins com- I,

bined and reacted in a specific manner.

It is another object of the present invention to provide a tough rubbery polyarnide resinous composition having excellent properties of solvent resistance and adhesiveness for bonding to wood, metal, fiber, and other materials.

It is a further object of the present inventionto provide a process of preparing the above product.

While the products of the present invention are otgeneral utility as adhesives and otherwise, they are particularly adapted for use as adhesives or cements for sealing seams in metallic containers. In this respect they may be used to replace metallic cements, such as solders.

In making metallic containers, such as cans, the operation is highly mechanized and automatic devices are used which serve to form and shape the parts and to bring the parts together for formation of seams. These devices are mechanically timed and operate at high rates of speed. Successive parts to be joined follow one another in very short intervals. Moreover automaticcan-making machines are equipped with thermostatically controlled heaters which heat the adhesive to a specific and limited temperature range at which the adhesive is soft or liquid. It is essential therefore that the adhesive at this temperature be sufiiciently soft andhave suitable viscosity'characteristics such that it will 2,839,219 Patented June 17, 1958 flow onto the seam portion of the can and such that it will develop adhesive characteristics within a certain limited period of time. It is essential not only that the adhesive possess the requisite adhesive characteristics but also that these characteristics do not change when a quantity of the adhesive is held in the molten condition for a considerable period of time. For example, there should be no appreciable change in the melting point of the adhesive while it is being held at application temperature since this might afiect the ability f the adhesive to adhere to the can part or its ability to set up within the required short interval involved in the seam making operation.

in addition to these melting point characteristics an adhesive intended for this type of application must possess other physical and chemical characteristics. The material should be tough and resilient so that the seams will not fail when the can is subjected to the ordinary handling in manufacture, packing and shipping.

Furthermore, the adhesive should be resistant to the materials which are packed in the can. Thus in the case of cans for food products the adhesive should not in any Way be affected by the food products nor should the adhesive be in any way toxic. In the case of cans for solvents and oils the adhesive should not be soluble in these materials but should retain its adhesive properties under these circumstances.

The compositions of the present invention are well suited for these applications either as adhesives for interfolded side seams of sheet metal containers or as gasket material for the end seams of sheet metal containers. The adhesive may be used on enameled or coated steel or tin plate or for uncoated steel or tin plate, aluminum, copper, and bronze. The products are heat stable and relatively little change in melting point is observed as the product is held in the molten state for an extended period of time. The adhesive is nontoxic and accordingly can be used in the seams of food containers, likewise, it possesses the requisite adhesive and cohesive strength for these applications. In addition the material is tough and resilient and does not tend to be brittle. In this way can seams remain intact during the usual conditions of handling both in the fabrication of the can 'as well as in the packing of the can and its shipment through the ordinary channels of distribution. The adhesive likewise is relatively inert to materials like lubricating oils, alcohols, and numerous other solvents and accordingly containers fabricated with these seams may be used for handling products of this nature.

As was pointed out above, the composition of the present invention is composed of a blend of two polyamides, hereinafter referred to as Resin A and Resin B. It has been discovered that by heat bodying Resin A, i. e. holding the resin in a molten state for a period of time to effect an increase in its viscosity, and thereafter combining it with a lesser portion of Resin B and heat treating the mixture in a manner more fully described, hereinafter, an adhesive composition results which not only has the desirable properties described above but is also superior to similar prior polyamide resin adhesives.

Both of these resins are prepared at least in. part from polymeric fat acids These polymeric fat acids may be either saturated or'unsaturated and may be derived by the thermal polymerizationor catalytic polymerization of higher fatty acids such as those having 12 to 22 carbon atoms. Acids derived from drying or semi-drying oils are especially suitable and include soybean, linseed, tong, perilla, oiticia, cottonseed, corn, tall, sunflower, safflower, dehydrated castor oil acids and the like. Linoleic acid is widely available from natural sources and is es ecially suitable for preparation of polymeric fat olefinic acids such as oleic may also be dimerized for this acid. Monopurpose but usually by a catalytic process.

Th po ym i atas d i i ual y ob ained m a r t ree of fat acids willjbe composed of a very large proportion-of dimeric fat acids together with some higher polymeric fat acidsand some residual monomer. QSome monomer is desirable in the mixed acidsfor the purpose of controllingpolymer size in the polyamide reaction;

cond y min roups-a sepa a e by sh chain a" vlcu oup h vin '2 to :c atoms The of equivalents of polyjamine to equivalentspf carbonyl Holdt viscosity scale as determined on a 35% solution by weight in'sbutanol-toluene, 1-1 or an increase of approxishould be such that cross linking aud hence gelation are a avq ds For eX Ple uth a c o d e y s tr e ns a r ti of e uiva en ro ram net 1 q iv len o car a v is referr d takin i c oun the e er in th p lvs c'fa c m x ur n ud n monsmsrs b We le the-h he Po y e pre en In e asedtrieth lsneeuami h r m n t c uc as 2.6 equivalents of amine per equivalent of carboxyl' is preferred. In general, the higher the amine functionahty of the polyami e the higher. the ratio-of amine equiva- .lents per carbonyl equivalent that is required to produce a ne ng-P9 e id Ass insly h P rt c a ex of amineto be emplpyed in each instance can readily be determined. Usually'it is not necessary to go outside the.

range 0511.3 to 3.0 eguivalents of amine per equivalent of carboxyl. r .s r V The polymeric fatfacids either in the form of the free acid or in the form of the lower alkyl esters thereof are reacted with the polyalkylene polyamine at a temperature ofaroirnd200 Cr After about '2 hours atthis reaction aminegroups :are also involved in the reaction. 7

' temperature the reactionmixture is subjected to a vacuum for the purpose ofremoving the volatile by-products of 7 reaction. The'condensation involves principallythe-pri- I 1 mary amine groups .but to some extent the. secondary At room ltemperature theseiresins are soft, tacky. and I resistant to greasespoils, water, water vapor, alkali, canpackingsbriiiesand syrups,- and a. number of organic solvents. .The' 'resins have an average'molecular weight within the. rangeof 2,500 to 6,500 and an acid number usually below 10. f

'In accordance with the present invention, it has been found that it .is possible to modify markedly' the characteristics of this resin by: subjecting it to'thebodying treatment following'the' condcnsationf As wasipointed out above the condensation reactiondoes tosome appreciable ente-nt:

involve the secondary -amine 'groupsas well as the primary amine groups. .It'hasbeen found thatby subjecting 'the resin to a bodying treatment at anelevatedtempcrature within thefapproximate range of ZOO-300 .C. for a period of from 63 ,0 hours,.it is possible to efiect amide interchange between the secondary and primary amine V groups within Resin A' itself such that the characteristics of the resin are materially modified. It is found that the 1 numberof free secondary amine groups inthepolyamide increases materially while, the number of free primaryamine; groups decreases materially. V The bodying is accompanied by some slight reduction in the acid number but this is notapprcciable. bodyingtreatment also afiec ts. the physical properties of'the resinpit is found that there is a significant change in'the viscosity of the es -Q sg n rsas inlr sspsi y a .ak 0f h qdying-treatment, may befroni l to 2 letters on the Gardner- 7 secnringahomogeneous reaction mixture and accordingly melting point of the copolymer resin may vary} wit mately 200 cps, on The Brookfield scale"( R. P. M. r 370? F. #4 spindle); It has been determined that for the purpose of the present invention the preferred com positions are those in which Resin A has been heat bodied cially those bodied to between D and E. a

This bodying of the Resin A also improves the charac tr "s or" the blend of polyamides in that an adhesive co; "15 this bodied Resin A forms bonds which are materially stronger than an adhesive which contained'unto a'Gardner-Holdt viscosity between C andF. and cspe bodied Resin A of the same viscosity, wherein the viscosity was attained by a slight adjustment in the propor of reactants. Thus a polyamide that has obtained a given viscosity as a result of bodying treatment subsequent ts the condensation reaction possesses superior properties as compared to the identical un b odied polyamide and as compared to'a polyamide whichh ttairied .the same viscosity during theIcondensation r'eaitojt;

through the use of modified reactant ratios.

' RESIN B ResinB 'is a high-melting. rit'tle polyamidefresinhefi rived from a mixture of "polymeric fat acids similar to those used in preparing Resin A and an additionaljpoly-j carboxylic acid, the latter having at least '2. carbonyl groups which are separated by at least,3 and: notquot"? thanS carbon atoms; Typical of such p'olybasic acids arethe aliphatic a'cids, glutaric, adip'ic; pimelic, suberic, f

azelaic, and sehacic, and the aromatic acidsg'terephtba lic and isophthalic'acids; Insteadfof thejfrice acids, thel oweraliphatic esters or the anhydrides may housed. 1;

range of l'302l0 C. depending uponthe particular tive reactant ratios as Well as reactionconditionsi De able copolymersfrom adipic acid melt at 200-2055: A from sebacic aciclat l7( )19 0 C.; and from terephth' acid at 165-170? 'C. In general these copolym po amide Resins B are prepared from a mixture ofpoycar-l; boXylic acids containing from 85-98% hy o/eight of tty. polymeric acids and'fromq-2.l5 by weightjof tional polycarboxylic acids.

In the. preparation of Resin B the 'niiietn of l qi ej basic acids is reacted with an allgylene dia "rn wh ch the alkyleiie radical has from 2 m4 carbon 'atonrs uch as ethylene diarnine; -1;2-' and '1,3-di amino propane;.1225 l,3-, and IA-di amino-butane, and the likei 'lfheireac nts? are mixed in approximately equivalent quantities and heated under essentially-the same conditions ashave' beeu described for Resin A. 'However, when the crondensatign is substantially complete there is no need'for subjecting Resin B to a bodying treatment although this is permissible. a t

Resin B at room temperature is a very hard copolyriier, which has-good resistance to greases, oil s, waterandwater vapor,'alkalies, mild acids, can-packing brin es'andsyrupsQ alcohols, and most organic solvents. Iliefaverage molec'u lar'weight'of Resin B is from 7,090 to 10,000;

Resin A and Resin B are then blendedand'subjected to an additional amide interchange reaction betwe en thc 1 amino groups of both resins. For this purpose thefresins are mixed in the relative proportions cinemas-7 5% of Resin A'and from -40% ofResin B and p referably in the proportion 0565 of Resin A to .of Rtsih Bs After extensive experimentation it was found'th-atfif'the V amounti of R esin- Ais greater-than of the tempest;

tio'n the resultingadhesive is too soft and lackisjsulfiicieat cohesive strength, while ifthe amount oflBesjn A is less I than'60% of the composition the .resulting adhesiveis harder and lessflexible.

' The blending ppe ation is for, t e asses it -m ea i d. u nrman w ys :Sisss tswsser hi desirable to have the amide interchangereactioutake' assaere place uniformlyit is preferred to efiect a homogeneous blend of the 2 resins as rapidly as possible. For this purpose it is preferred to melt the lower melting Resin A and to disperse in this molten Resin A particles or pieces of resin B. These pieces should be egg size or smaller so that they will liquify rapidly and form a homogeneous mixture before any substantial quantity of Resin B which has first gone into solution, has had an opportunity to react with the resin A. The mixture is subjected to agitation to insure a homogeneous blend and the surface of the blended resins is maintained under an inert atmosphere to prevent oxidative deterioration.

Satisfactory blending can be accomplished at temperatures in the approximate range of ZOO-300 C. andpreferably within the approximate range of 200-220 C. If blending is done below 200 C. the components lack sufficient fluidity for intimate mixing whereby a non-homogeneous composition results. When such non-homogeneous blends are then held molten at temperatures close to the melting point of the composition the higher melting Resin B has a tendency to separate and form gel particles in the mass. If too high a temperature is maintained during blending, the first portions of Resin B to melt may take part in the amide interchange reaction to some degree before the entire amount of Resin B becomes'molten, and accordingly a non-uniform product may result.

During the blending operation it is necessary only to allow sufiicient time to insure a homogeneous blend. The time interval is dependent upon the temperature of blending, the size of the Resin 3 pieces added, and the efiiciency of agitation. We have found that by adding egg sized or smaller pieces of Resin B to molten Resin A at about 200 C. using a mechanically operated agitator a time interval of about 30-60 min. is sufficient.

The amideinterchange reaction between Resin A and Resin B takes place readily at temperatures above approximately 200 C. and is accompanied by a rather rapid reduction in the melting point of the blends. As equilibrium is approached there is a sharp decline in the rate at which the melting point drops and consequently there is a leveling oflf in the curve obtained by plotting melting points against time. The product thus has a relatively stable melting point.

Further reaction is possible between the two resins which would to some extent result in a further melting point drop but the rate, of this drop in melting point is very low.

A suitable temperature range for the amide interchange reaction is the range of ZOO-220 C. At 200 C. a

period of about 16 hours is suitable while at 220 C. a

time of about 1 hour is generally sufiicient.

In order to determine a suitable. time period at any given temperature the reaction may be carried on as follows: The blend of resins is held at a suitable reaction temperature and a sample withdrawn at short inter vals during the process for the determination of a melting point. By following the course of the reduction in melting point'it is possible to determine the point at which the rate of melting point drop decreases sharply. Heating is then discontinued and the resin composition is removed from the reaction vesse] and packaged for subsequent use.

Example 1 RESIN A 7,615 pounds polymeric fatty acids, 456 pounds of monomeric unsaturated fatty acids, and 1520 pounds of diethylene triamine were placed in a reaction vessel. The

6 resin was then maintained in the reaction vessel at approximately 205 C. for 16 hours additional at which time it had attained a D viscosity.

RESIN B In a reaction vessel a uniform blend of acids containing 288.2parts of polymeric fat acids, 31.7 parts of monomeric cottonseed fatty acids, and 31.7 parts of sebacic' acid was heated to a temperature of about C.- Ethylene diamine (57 parts of 74.5%) was then added and the whole mixture raised to a temperature of about 200 C. The reaction mass was agitated to insure intimate contact of the several ingredients. The intimate mixture was maintained at approximately 200 C. for a total of about 4 hours, thelast 2 hours of which it was maintained under reduced pressure. The vacuum was then broken by means of an inert gas and the heating discontinued. The product was filled into suitable containers and allowed to solidify.

65 parts of Resin A were placed in a closed reaction vessel equipped with a mechanical agitator. The charge was blanketed with an atmosphere of nitrogen and heat applied to the kettle to raise the temperature of approximately 200 C. Thereupon 35 parts of Resin B which had been reduced to egg size or smaller were charged into the kettle over a period of about minutes while the kettle was maintained at approximately 220 C. The mixture was agitated during this period and after all of Resin B had been added, the heating was discontinued and the mixture was allowed to cool to 213 C. at which temperature it was maintained and agitated for an additional 180 minutes. Heating and agitation were then discontinued and the temperature of the blend allowed to drop to 209 C. The vacuum was then broken and the product packaged'off.

After all of the Resin B had been added, the course of the amide interchange reaction was observed by removing a sample at intervals and checking its melting point. At the time all the Resin B had been added the blend was found to have a melting point of 192 C. and the time interval was measured from this point. The results are tabulated as follows, the time being the total elapsed time.

Time (minutes): Melting point C.)

Atthis point the reaction was assumed to have reached equilibrium. The heating and agitation were then discontinued and the product allowed to cool preparatory to packaging it ofi. The melting point of the packaged material was found to be about 181 C. thereby indicating that equilibrium had been reached and that the melting point of the composition was substantially stable.

Example 2 Viscosity, Gardner-Holdt A-2 Acid No 5.5 Amine -No 221.7 Percent primary amine 51.1 Percent secondary amine 48.9

This product was then heated to 200 C. under a V vacuum of '10 mm. with agitation for /2 hours. At this point the product had "the following properties:

Viscosity Gardner-Holdt A-l Acid No 3.5 Amine ,NO-- 208- Percent primary amine 49.5

Percent secondary amine; 50.5 The product was then bodied further. It was heated to a temperature of 200210 C. for an additional 12' hours under a vacuum of 15 in. of mercury, with agi- This resin may be substituted for the Resin Adescribed in'Example 1 anda bodied blend prepared from the mixture of this resinand Resin B to. produce an ultimate adhesive which has similar properties to' the final product of Example 1.

For the prope-rties'listedtherein, the table below shows the difference between a blend of 65 parts of Resin A an rt Rss n Br Pe e ac o n o the present invention and the same blend not .so jprepared Column I gives the data relative to a blendof Resin 3 with a nonheatbodied Resin A, the'Resin A having a viscosity of about 200 cpjor A onthe Gardner-Holdt- Column II gives the data1rel ativejto"a blend scale. similar to that in'column I except that :the ResinA- ofl has been heat bodied as described hereinbefore ;;to ;a

viscosity of.690 cp..oriD on the Gardner-Holdt scale r or c l udi s i h R s B- iEroperty V I II;

Dennis Bar, M. P., F. (initial 370 370 Dennis Bar, M. P.,' F. (after heating for 3 hours at t 420 F.) 340 -3i0 Rate of M. -P. decline whenheld for 6 hours at 370" F. 1 p

' in F. per hour (heat treated-blend) 3.0 2

Viscosity change during 6 hour heating above. 0 Mconey'viscosity at 190 F. for a 2 minute ran 13. 5 23: Mooney elastic recovery at,l90 F. ior sec.-. 26 35 Hex hardness at in; 90 Pell strength at angleofbonded sheet metal strips pulled over rollers in pounds per A lineal inch 18. 3. 27. 5

product of a polymeric 'fatac'id and a 'polyalkylene polyaminefthe'polyalkylene polyamine being employed in a ratio of 1.3 to 3.0 e'quivalents of amineper equiv a lent of carboxylic acid, said Resin A having been'sub amide'Resin 'B which is the .re'actionproduct off-'ani alkylene diamine and -a mixture of a polymeric 'fat'acid' and a polycarboxylic acid selected from the group con alkylenev diamineand amixture .of a polymeric fat acid: and. a polycarb'oxylic' acid'selected from the group con-' sis'ting of aliphatic andaromatic.polycarboxylicacids' in which-the carboxyl groups are separated by from 3 to 8 carbon atoms, the'blend of Resin A and Resin B having.

been treated 'at a temperature withingthe approximate range of 200 to220 C. for a time sufiicient to efiect' an amide interchange between the resins. A

2. YA productaccording to'claim 1 in which the polyalkylene polyamine is diethylene triamine, the alkylene diamine is ethylene diamine, and the polycarboxylic acid' is sebacic acid.

3. A plurality of metal layers selected from the group consistingof steel, aluminum, copper and bronze having the composition of; claim '1 between adjacentsurfaces of said layers asza hermetic bondingmaterialV V 4. A plurality of tin plate layers having the as a hermetic bonding material.

a hermetic bonding material." s 6. A container made vof a metalselected from the group consisting of steel, aluminum, copper and bronze 7 having the composition of claim '1 interposed between interfolded metal layers composing a -seamjof said container.

, 7. A method of forming af'homogeneous resin compo- I sition having a substantially stable melting pointwhen 'held in a molten :state, comprising intimately'blending a polya'mide Resin A which is the reaction product of 'a polymeric; fat acid and a polyalkylene polyamine, the

polyalkylene polyamine being employed inla' ratioofliil .to 3. 0 equivalents of amine per equivalent of carboxylic acid, said Resin A having .been subjectedv to abodying treatment ;-at 20.0,".10'300. 'C. totefiiect' an increase in f Gardner-Holdt viscosityof atleast one letter, with polysisting of'aliphatic and aromatic polycarboxylio acidsin which the ,carboxyl' groups 'areseparated byfr om 3 to 8- carbon atoms,v and subjecting the 'blend to a temperature" within the 'approximaterange of 200. to 220 C.'for"a time sufiicient to eifect an amide interchange reaction V between'the 'resins. I 1 r jected to a bodying treatment at 200 to 300 C. to 1 effect an increase in Gardner-Holdt viscosity of at' least one'letter, 'saidResin B being the reaction product of an 8. Process 'according to 'claim alkylene polyamine is diethylene triamine, the. alkylene V diaminfeis ethylene diamine, and .the'polycarboxylic acid is sebacic acid. 7 7

References Cited inlthe fileiof this patent V UNITED STATES PATENTS 2,339,237

V OTHER REF REN ES Anderson .et aluf]. Chem. Soc 70,.February 1948, pp. 7605763.

, lOilandSoap, 21. April 1944, 101407.

V I composition of claim '1 between adjacent surfaces of said layers.

7f in 'vjvhich the pay-f: 

1. A RESIN COMPOSITION HAVING A SUBSTANTIALLY STABLE MELTING POINT WHEN HELD IN A MOLTEN STATE, COMPRISING A HOMOGENEOUS BLEND OF FROM 60 TO 75% BY WEIGHT OF POLYAMIDE RESIN A AND FROM 25 TO 40% BY WEIGHT OF A POLYAMIDE RESIN B, SAID RESIN A BEING THE REACTION PRODUCT OF A POLYMERIC FAT ACID AND A POLYALKLENE POLYAMINE, THE POLYALKYLENE POLYAMINE BEING EMPLOYED IN A RATIO OF 1.3 TO 3.0 EQUIVALENTS OF AMINE PER EQUIVALENT OF CARBOXYLIC ACID, SAID RESIN A HAVING BEEN SUBJECTD TO A BODYING TREATMENT AT 200* TO 300*C. TO EFFECT AN INCREASE IN GARDNER-HOLDT VISCOSITY OF AT LEAST ONE LETTER, SAID RESIN B BEING THE REACTION PRODUCT OF AN ALKYLENE DIAMINE AND A MIXTURE OF A POLYMERIC FAT ACID AND A POLYCARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC AND AROMATIC POLYCARBOXYLIC ACIDS IN WHICH THE CARBOXYL GROUPS ARE SEPARATED BY FROM 3 TO 8 CARBON ATOMS, THE BLEND OF RESIN A AND RESIN B HAVING BEEN TREATED AT A TEMPERATURE WITHIN THE APPROXIMATE RANGE OF 200* TO 220*C. FOR A TIME SUFFICIENT TO EFFECT AN AMIDE INTERCHANGE BETWEEN THE RESINS. 